midnightjeeper

So, I am at my wits end with this thing...

1995 Jeep XJ 4.0 has been running a bit hot (220-230) under heavy loads (mudding and wheeling) and at highway speeds (55+). Never has overheated but has touched the red and went right back down or I just stop and let it cool down. I just had the radiator start leaking on me and I thought great chance to throw a 3 row radiator in it and keep it a little cooler right, WRONG. Installed a CSF 3 row radiator and ran it last night and this AM, seems to be getting hotter faster now and I cannot put my hands on the problem.

I have on the jeep an electric fan conversion with a two speed fan, fan kicks on first at 160-170 with a switch, then second can be turned on by me manually or by the 180 degree switch mounted in the radiator.

Normally the 2nd speed does not kick on by itself unless wheeling, but recently it has been running more and my thoughts were that the 3 row would help the system stay cooler, right?

1. I am not loosing fluid and the motor is not smoking.
2. I bought a Combustion gas leak kit from Napa to check for exhaust gases in the radiator and it tested good and showed no signs of leaks.
3. I have a 160 degree thermostat. At idle ever goes up past 180, cruising it will stay around 210.
4. I have a transmission cooler added to the one already installed in the radiator, it's the OCD in me...lol
5. The heater seems to be working well and blows hot and cools the truck off if I run it when it starts to get hot.
6. It has never puked its fluid either into the catch can nor on the ground while at it's hottest!

I went out today and bought a New water pump, New Heater valve, New upper and lower hoses and another new belt. Hope that one of these items will be the culprit that is screwing with my head...

I also burped the system by parking the truck facing down hill and unscrewed the temp sensor to allow the air to escape...Here is where it struck me odd and correct me if I am wrong, I was able to unscrew the temp sensor all the way and take it out without being sprayed in the face by warm/hot coolant. Shouldn't this have sprayed out like a bat out of hell if I took the sensor completely out and the cooling system was under pressure? Even with the cap off and the water pump running, with a full system, would it or would it not spray it out the hole until plugged?

Help and thoughts/experience is appreciated. I don't know where it go next!

tjwalker

Get that new water pump installed. It may very well be the root cause.

A 95 should burp itself in about 3-4 complete heat up / cool down cycles.

Only thing I didn't see mentioned was radiator cap. May as well be sure it is fresh too.

midnightjeeper

I did not mention it but it has a 16lbs cap on it and I just replaced it with a 13lbs cap which is what the Stant book stated for my year.

I am thinking that may be the reason that it is getting hotter faster due to the lowered boiling point with the 13lbs cap.
Does that sound correct?
Are the Stant brand caps any good?

letsgomuddin

I bet it's the water pump. I usually let a 4.0 run for about a half hour with the cap off after changing the water pump to burp the air out of it. Just keep the coolant full while its warming up and you will have no air pockets.

midnightjeeper

Would the Combustion gas test show a cracked head or block? That was my other concern. I have never ran the vehicle hot or Extremely hard, so I wouldn't know why it would be cracked unless it was like that when purchased, but again, I am using no fluid therefore it wouldn't be that would it?

I am just dumbfounded at this...

djb383

Seems like it would be best to park it facing up hill or at least on level ground. The front of the motor is slightly higher than the back of the motor....air naturally rises to the highest point, which is the front of the motor and the front of the motor is where coolant (and air) exits.

If coolant doesn't come out the sending unit hole, the hole could be plugged with crud below the sending unit OR coolant level in the motor is really low. Stick a piece of wire in the hole to break up crud and see if coolant will flow out. If the hole is crudded up, it's likely the whole system is crudded up. Hope the water pump doesn't look like this.

midnightjeeper

I could see the water "Kind of moving" in through the sensor hole and it would even touch the top of the sensor hole threads, just never ran out or gushed out. I had helped a buddy burp his in the past and the coolant came out like a Mother, thankfully it wasn't to hot yet, still hot enough to get your attention. Just seemed odd that mine did not do this when I bleed the same way...

nickxj94

I would put a 190 t stat in and try that that's what is recommended for the 4.0 anyways, that new radiator is it metal?or aluminum? I heard metal is better for cooling..

midnightjeeper

A 160 stat should keep the engine cooler then the stock 190 stat, No?

The new radiator is aluminum and brass, tried to get a magnet to stick to it and it would not grab anywhere!!

djb383

A 13lb cap raises the boiling point of water from 212 to 251....a 16lb cap raises it to 260....not enough difference to be concerned with.

If the cooling system is full, there should be a momentary gusher out that hole the second the motor starts.

Aluminum is metal, no?

djb383

A properly functioning t-stat does one thing, maintain MINIMUM coolant temp. The XJ has a really dinky radiator and during the winter months a 160 stat will make for cooler temps vs a 190 stat however, during the summer months, a 160 stat is NOT likely to make the motor run cooler. All of the other cooling system components and their condition along with ambient temps and driving conditions determine MAX coolant temp.

I believe the CSF rads are copper/brass construction. OE rads are aluminum/plastic construction.

midnightjeeper

Thats what I thought about the cap!!

The system would not take any more water and I then put the cap on, removed the sensor and nothing, should be under enough flow/pressure to push the water out at any time, correct??

I always thought aluminum was a form of metal, I didn't pay that much attention in grade school but I did hear that part...lol

midnightjeeper

I like to keep it cooler and it was never cool enough for me with the 190 stat so I went to a 160 to keep it down a little farther, worked for a while...

djb383

Like I said, a gusher.......the water pump, Git 'er done.

djb383

Being in So. Central Florida, a 160 stat u can probably get by with. FWIW, I would never recommend lower than a 180.